MANILA, Philippines (AP) — The U.S. military has deployed the third aircraft carrier this year to patrol the disputed South China Sea, where Washington has criticized China’s military buildup on new man-made islands.

The 97,000-ton USS Ronald Reagan, carrying more than 70 aircraft, anchored in Manila Bay on Tuesday after plying the strategic waters for meetings between navy officials of the two countries and liberty for its thousands of sailors after weeks at sea.

The U.S. military presence in the region “has supported our ability to defend our nation and our allies” and “promotes our ability to safeguard freedom of the seas, unimpeded commerce, to deter conflict and coercion and to promote adherence to rules-based international order,” Rear Admiral Marc Dalton told reporters on board the ship.

Two other American carriers earlier patrolled the waterway, where China and five other governments have been locked in decades of disputes over territories that straddle some of the world’s busiest sea lanes. Some areas are believed to have undersea deposits of natural gas and oil.

China has reportedly deployed anti-ship missiles, surface-to-air missiles, electronic jammers and other equipment on islands it built on disputed reefs in the Spratly Islands, and landed a bomber aircraft on Woody Island in the Paracels, sparking alarm among rival claimants and the United States. Washington has no territorial claims in the region but has declared that freedom of navigation and overflight in the waters is in U.S. national interest.

U.S. Defense Secretary Jim Mattis said earlier this month that the Trump administration’s recent decision to disinvite China from a multinational naval exercise this summer was an “initial response” to Beijing’s island activity. Mattis called the U.S. action a “relatively small consequence. I believe there are much larger consequences in the future.”

China argues that it is within its rights to build up defenses on islands in the South China Sea that it claims are its sovereign territory. There is fear that Beijing will use its new islands, including some with runways, to project its military might and potentially to restrict navigation in the busy waters.